package umontreal.iro.lecuyer.hups;

/* *
 * Title:        

 * Description:  

 * Copyright:    Copyright (c) 

 * Company:      

 * @author
 * @version 1.0
 */
import umontreal.iro.lecuyer.util.PrintfFormat;

/**
 * This class implements Korobov lattices, which are the same point sets
 * as in class {@link LCGPointSet}, but implemented differently.
 * The parameters are the modulus n and the multiplier a, for arbitrary
 * integers 
 * 1 <= a < n. The number of points is n, their dimension is 
 * s, and they are defined by
 * 

 * 
 * 

 * ui = (i/n)(1, a, a2,…, as-1) mod 1
 * 

 * for 
 * i = 0,..., n - 1.
 * 
 * 

 * It is also possible to build a ``shifted'' Korobov lattice with the first
 * t coordinates rejected. The s-dimensionnal points are then defined as
 * 

 * 
 * 

 * ui = (i/n)(at, at+1, at+2,…, at+s-1) mod 1
 * 

 * for 
 * i = 0,..., n - 1 and fixed t.
 * 
 */
public class KorobovLattice extends Rank1Lattice  {
   protected int genA;                        // Multiplier a.

   // Method modPower is inherited from Rank1Lattice.


   /**
    * Instantiates a Korobov lattice point set with modulus n and 
    *    multiplier a in dimension s.
    * 
    */
   public KorobovLattice (int n, int a, int s)  {
      super (n, null, 0);
      if (a < 1 || a >= n) 
         throw new IllegalArgumentException 
            ("KorobovLattice must have 1 <= a < n");
      genA = a;
      dim = s;
      v = new double[s];
      long[] B = new long[dim];
      B[0] = 1;
      v[0] = normFactor;
      for (int j = 1; j < dim; j++) {
         B[j] = (a * B[j - 1]) % n;
         v[j] = normFactor * B[j];
      }
   }


   /**
    * Instantiates a shifted Korobov lattice point set with modulus n and 
    *    multiplier a in dimension s. The first t coordinates of a
    *    standard Korobov lattice are dropped as described above.
    *    The case t = 0 corresponds to the standard  Korobov lattice.
    * 
    */
   public KorobovLattice (int n, int a, int s, int t)  {
      super (n, null, 0);
      if (a < 1 || a >= n) 
         throw new IllegalArgumentException 
            ("KorobovLattice must have 1 <= a < n");
      if (t < 1) 
         throw new IllegalArgumentException 
            ("KorobovLattice: must have 0 < t");
      dim = s;
      genA = a;
      v = new double[s];
      long[] B = new long[dim];
      int j;
      B[0] = a;
      for (j = 1; j < t; j++)
         B[0] *= a;
      v[0] = B[0] * normFactor;
      for (j = 1; j < dim; j++) {
         B[j] = (a * B[j - 1]) % n;
         v[j] = normFactor * B[j];
      }
   }


   /**
    * Returns the multiplier a of the lattice.
    * 
    */
   public int getA()  {
      return genA;
   }



   public String toString() {
      StringBuffer sb = new StringBuffer ("KorobovLattice:" +
                                           PrintfFormat.NEWLINE);
      sb.append ("Multiplier a: " + genA + PrintfFormat.NEWLINE);
      sb.append (super.toString());
      return sb.toString();
   }
}